The biggest problem with writing a one-joke show is also the most obvious: keeping the initially arresting thread of hilarity snaking through every scene, ending only when the story itself does. Against the odds, this is what Fred Sauter and Paul Leschen have managed with BEDBUGS!!! (capitals and punctuation theirs).

The one joke is that, in 2012, the 1980s have returned with a ridiculous vengeance. Not only have the individual members of the titular infestation afflicting New York mutated into six-foot-tall rock stars, but day-to-day life has similarly transformed into a parodically bloody Wes Craven horror flick. The first scene, set in 1989, in which a young girl named Carly (Celina Carvajal) rocks out to the incomprehensible debut of big-haired Canadian pop diva Dionne Salon (Brian Charles Rooney) while Carly’s mother dies after an assault by Yugoslavian bedbugs, sets a standard for plot-propelled comedy you think no future scene could match.

Not so. BEDBUGS!!! builds upon every preceding scene sturdily enough to suggest that librettist-lyricist Sauter could pursue an alternate career as an architect if he so chose. (He shouldn’t.) Carly grows up to be a scientist obsessed with inflicting genocide on all bedbugs, at any cost; her Silent Spring-reading assistant Burt (Ryan Bogner) prefers to kill them with planet-friendly chemicals. Carly doesn’t listen, and her experimental extermination methods lead to not only the anthropomorphic bugs, but also the establishment of their David Lee Roth-like leader, Cimex (Chris Hall), who’s determined to take Carly as his queen.

Scarcely a minute passes without some solid-gold sight gag or astounding, throat-stretching song testing your tolerance for 80s nostalgia in a way even VH1 has never dared. Throbbingly silly depictions of insectoid homosexuality. Explosively cinematic direction (by Samuel Buggeln) and fine-cheesy choreography (by Robin Carrigan) that captures with freeze-dried giddiness the best of the worst dance moves two decades behind the times. Dionne’s howlingly horrific numbers, which the priceless Rooney (clad in glittering drag from costume designers Amanda Bujak and Chris Rumery) croons, croaks, and screeches to shattering perfection.

Rooney’s costars are similarly expert, with Carvajal (late of the Legally Blonde recasting reality show) unleashing a thrillingly intense voice and a fiery, frantic comic sense, Hall finding every delectable ounce of squirm in his sexaholic metal-star arthropod, and Bogner bringing a flamboyant innocence to the (vaguely) straight man struggling to control his own burgeoning passions. Tracey Gilbert, Mark Fisher, H. Wayne Williams, and Stephen Sheffer, playing the bugs and other scurrying roles, are masters of quick-change characterizations, and every bit the leads’ equals.

Some tightening, particularly in the overlong first act, and another draft of some scenes, particularly in the second, would help better focus existing laughs. But not much work needs to be done: With Sauter’s burrowing and boisterous book and lyrics, Leschen’s invidiously astute 80s take-off tunes, and such strong performers on hand, BEDBUGS!!! already has almost all the bite it needs.

When was it decreed that children’s musicals must aim no higher than to be object lessons in overacting and compendiums of adults’ funny voices? The creators of Max & the Truffle Pig are adhering to the letter of that mysterious ruling with a zealousness that would startle even die-hard law-and-order types.

Basing their work on Judith Gwyn Brown’s 1963 children’s book, bookwriter Suzanne Bradbeer, lyricist Nancy Leeds, and composer Bert Draesel tell the unconventional love story of a boy, Max (Kevin Michael Murphy) and his new pig, Suzette (Jennifer Albano), who discover their purposes in life while on a fungus-digging adventure for Max’s blustery chef father Gerard (Jeremy Schwartz). Suzette isn’t really a truffle pig; in fact, she can’t stand dirt at all. But the local Comtesse (Antoinette LaVecchia) has a hankering for truffle cake, and her approval could make Gerard’s name.

There’s a latent sweetness between Max and Suzette, who bond beneath burdens of expectations no adult person or pig could likely meet. And as long as the story stays focused on Max’s instilling the lackadaisical Suzette with self-confidence and the emboldening affection Suzette gives him in return, the show is affectingly cute. Murphy’s more than a little cloying, but he’s a good-natured hero; Albano’s all-consuming disinterest takes time to develop into a more completely colored portrayal, but ends up a winning portrayal.

But every new character threatens that fragile balance, piling on plodding accents and sweeping surface emotionalism until Max & the Truffle Pig feels like a moldy college skit put on by undirected freshmen. No one piles it on thicker or slicker than LaVecchia, whose French-fried Comtesse consists of nothing more than melodic whinnying and adding more vowels to her words than a contestant during a Wheel of Fortune bonus round. Cindy Cheung plays her maid, Ethel, with a half-tempered version of the same shtick. Schwartz’s performance seems to have been lifted directly from the movie Ratatouille; Rob Skolits, in a trio of cameo chorus roles, is only marginally more real.

Director-choreographer Erica Gould maintains just enough fantasy in her mechanically lively production to keep the whimsy just this side of plausible, and the songs grow from tritely tuneful to touching as Max and Suzette’s friendship blossoms. But the actors’ conflicting styles support the idea of moderately realistic fairy tale less than they do the kind of out-of-control, robotic romp that even the youngest theatregoers tend to outgrow before they take their seats.